Similarities of 34 CVID and 398 IgGSD patients referred to a hematology/oncology practice determined using univariable analyses included specialties of referring physicians, mean ages at diagnosis, proportions of women, reactivity to Pneumovax, median serum IgG3 and IgG4 levels, median levels of CD56+/CD16+ blood lymphocytes, positivity for HLA-A and -B types, and frequencies of selected HLA-A, -B haplotypes. Here, NCAM1 is linked to common variable immunodeficiency.